The display of merchandise in stores and supermarkets often involves the use of trays in which products are placed in columns and continuously urged to the front by spring-driven pushers. Such trays often are mounted in a cantilever fashion, by means of display bar assemblies carried by a store's merchandising structures, such as gondolas. An advantageous form of such trays, which are in widespread use, is illustrated in U.S. Pat. No. 8,210,367, owned by Trion Industries, Inc. An advantageous means for the mounting of such trays is shown in U.S. Pat. Nos. 7,404,533 and 7,438,268, also owned by Trion Industries. These patents disclose mounting bar assemblies in which square, tubular tray-mounting bars are provided at opposite ends with slidably movable mounting brackets. The brackets have mounting hooks that are engagable with slotted vertical uprights mounted on gondolas or other merchandising structures in the stores. The bar-mounting brackets are slidable to accommodate spacing variations between pairs of slotted uprights, and are captured on the bars by means of flanged retaining plugs inserted into opposite ends of the bars. While the systems of above-mentioned patents have been very successful, there has been currently increasing trend by merchandizers to display heavier merchandise. This can result in overloading of the standard cantilever-mounted trays and also the display bar assemblies for mounting them. There currently is a need for more robust display structures that can be made available to the trade without significant cost increase.